Vision Resources

This section contains interesting articles, checklists, charts and videos about vision and eye health. You can find hundreds of eye- and vision-related definitions in our glossary, explore our human eye anatomy chart, download brochures on the most popular eye health topics, and more.

Downloads: Brochures, Booklets, MoreHere you can download informational brochures and guides on pink eye, eye safety, allergies, eye nutrition and more. Some are great handouts for teachers and eye care practices.

This chameleon seems to be looking in two directions at once! [Enlarge]

Do Chameleon Eyes Work Together Or Separately?

You already know that chameleons can change color to match their environment. But they have another weird skill: they can point each eye in a different direction from the other. With this they have a wide field of vision, so they can perceive more of their surroundings with less body movement. This helps them be less visible to both their predators and their prey.

Still, scientists have wondered whether chameleon eyes actually see two distinct views. To test this, researchers in Israel showed each of their chameleons a double image of an insect moving in opposite directions across a computer screen. The chameleon would focus one eye on one insect but let the other eye look around. Then, both eyes would focus on one insect very briefly and the chameleon would shoot out its tongue to try to catch it.

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The researchers concluded that the eyes were not acting completely independently. There seemed to be a need for them to converge on the target once the chameleon had decided to attack, in order to get the proper depth perception for success. Also, the second eye seemed to know where the first eye was looking, since it was able to swivel around very quickly to the same target. The researchers called this a kind of "cross talk" between the eyes.

As Professor Ehud Rivlin of the Technion-Israel Institute of Technology said, "Each eye is aware of its own location and the orientation of the other eye. It is just a different kind of cooperation that takes place in human binocular vision."

A paper about the study appeared in the July 2015 issue of the Journal of Experimental Biology.  L.S.

Could Your Eye Color Predict Your Drinking Habits?

Research from the University of Vermont suggests that people with lighter colored eyes may be at a higher risk for alcoholism. The study examined a group of 1,263 European-American patients, including 992 people with alcohol dependency problems and 271 without alcohol problems.

Among the sample, those with light-colored eyes (blue, green, gray and light brown) had a 54 percent higher rate of alcohol dependence than that of people with dark-brown eyes. Those with blue eyes had the highest rate of alcohol dependency, about 80 percent higher than those with other eye colors.

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Interestingly, genetic analysis confirmed that the genes responsible for eye color and the genes related to alcoholism are found on the same chromosome.

Just because there is a correlation between eye color and alcoholism, does not mean that all blue-eyed people will be alcohol dependent. However, researchers hope that knowing more about the genetic traits linked to alcoholism will help people better understand their own risk factor.

The study was published in the American Journal of Medical Genetics in July 2015.  N.B.

Does How Well You Hear Influence How Well You See?

According to a 2015 study by life scientists at UCLA, our ability to accurately perceive where an object is located is surprisingly poor, yet is somewhat improved when auditory cues accompany visual ones.

Ladan Shams, PhD, an associate professor of psychology in the UCLA College, studied "spatial localization," or how well a person can immediately and accurately perceive where an object is. What she and her team discovered came as a bit of a shock.

The scientists played brief bursts of sound and triggered flashes of light, in various combinations, and asked 384 study participants to identify where they originated. In general, people fared poorly when the light and sound were played alone. And the ability to locate visual stimuli in the periphery was much worse than it was in the center of their visual field.

"We didn't expect these spatial errors; they're very counterintuitive," Shams said. "Spatial localization is one of the most basic tasks the brain performs."

It's interesting to note, however, that participants performed with improved accuracy when the flashes and noise were played simultaneously at the same location, indicating that how well you hear could affect how well you see, and vice-versa.

"The brain is wired to use information from multiple senses to correct other senses," Shams said. "The saying is true: 'If you want to hear better, put your glasses on.'"  A.H.